As during the past project period, the planned research concerns mainly the auditory system. One major part of the project deals experimentally and theoretically with the auditory periphery, including sound transmission in the middle and inner ear, sound transduction in the cochlear hair cells, and neural coding the cochlear nerve. Another part concerns more generally mechanoreception which will be studied on Pacinian corpuscles in addition to the hair cells. A third part is devoted to the study of summation among heterosensory sensation magnitudes. In the first part we plan to complement and verify our measurements of the input impedance and improve our derivation of the transmission characteristic of the human middle ear. We also plan to complement our measurements and analysis of the time and intensity characteristics of the stapedius-muscle reflex. Further, we plan a three-dimensional analysis of wave propagation and a theoretical and experimental study of interaction between the tectorial membrane and the hair cells in the cochlea. According to our preliminary work, the interaction may produce a substantial sharpening of cochlear frequency analysis and be chiefly responsible for such nonlinear phenomena as two-tone suppression and combination tones. Sound transduction in the cochlear hair cells will be studied by means of intracellular recordings for which the required techniques have recently become available. These studies, in connection with the tectorial-membranes, should tell us which aspects of the firing-rate characteristics seen in the cochlear nerve originate in cochlear mechanics and which in cochlear transduction processes. In addition, the cochlear-nerve studies will yield the aspects due to neural processes. The latter studies focus in particular on interaction between saturation and adaptation processes. The Pacinian-corpuscle work is expected to reveal functional details of mechanoreception, which may be applicable to the cochlear hair cels. Finally, the psychophysical studies on summation of heterosensory sensation magnitudes is expected to firm up our concept of sensory magnitudes.